The present invention relates generally to silicon-on-sapphire and silicon-on-insulator semiconductor processing, and more particularly to methods of forming doped edges on the sides of the mesas of such silicon-on-saphire and silicon-on-insulator semiconductors.
Conventional bulk CMOS semiconductor fabrication processes employ guard bands, or guard rings, to minimize leakage. However, conventional N-channel silicon-on-sapphire and silicon-on-insulator semiconductors have mesa structures in which no such guard bands are employed. Typically, no edge doping is performed, and the substrate is employed as a guard band in an attempt to prevent leakage. In radiation hard silicon-on-sapphire and silicon-on-insulator semiconductor devices it is necessary to heavily dope the mesa edges to eliminate edge leakage and threshold instability. In the past it has been difficult to dope these edges to achieve radiation hard device performance, for example.